Corrugation forming by explosives



L. KUNSAGI ETAL CORRUGATION FORMING BY EXPLOSIVES March 12, 19.68

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ATTORNEY iq/Z L. KUNSAGI ETAL CORRUGATION FORMING BY EXPLOSIVES March 12, 1968 4 Sheets-Sheet 5 Filedl April 1s, 1965 IT Z Y WN? M N/A aan# M0 KPREM r n TH e am WW1 M ML/MM. y 5

March 12, 1968 L. KUNSAGI ETAL 3,372,565

CORRUGATION FORMING BY EXPLOSIVES Filed April 15, 1965 l 4 sheets-sheen 4 J2SE/DH H HE/FE 7Z BYRAM J. MAJOL United States Patent 3,372,565 CORRUGATION FORMING BY EXPLOSIVES Laszlo Kunsagi, New York, N.Y., William R. Apblett, Metuchen, NJ., Irwin Berman, Bronx, N.Y., and Joseph H. Heifetz, Fort Lee, and Byram J. Magol, Convent, NJ., assignors to Foster Wheeler Corporation,

New York, N.Y., a corporation of New York Filed Apr. 13, 1965, Ser. No. 447,709

1S Claims. (Cl. 72-56) ABSTRACT F THE DISCLOSURE A method and apparatus for corrugating panels by the use of explosive wherein the explosive is limited in amount so that grooves in the panel are substantially free-formed.

This invention relates to the fabrication of high strength panels. In particular, it relates to a method involving free forming of high strength corrugated panels by explosive.

Corrugated paneling is advantageous from considerations of strength and design. In the past, heavy dies have been used to fabricate contoured panels in conjunction with both press formation, and with explosive formation. Where the panels to be formed are limited in number, the expense and inconvenience of die fabrication may be prohibitive. Even with the manufacture of a large number of panels, the cost of heavy dies may be a burden. Also, where the contour design configuration is changed from panel to panel or where the panel sizes vary, die formation is highly undesirable. A further -disadvantage is inherent in press formation methods utilized in conjunction with conventional dies, since panel shrinkage may occur making it impossible to pre-size the panel for installation prior to contour forming.

Therefore, it is an object of the present invention to provide economical and convenient methods for the manufacture of corrugated panels.

It is also an object of the present invention to provide a method in which the use of conventional contour or forming dies is avoided.

It is a further object of the present invention to provide a method for the production of ultra-high strength contoured panels which are exi-ble in the plane of the panel.

It is another object of the invention to provide a method by which panels can be pre-sized and subsequently formed, without altering the over-all panel size during forming.

In accordance with the present invention, shaped charges are supported against or closely adjacent to a panel to be formed, with major portions of the explosive along the lines of the contours to be produced, the shape an-d sizes of the charges being dictated by preselected shapes of the contours. The charges are simultaneously detonated in a suitable medium to develop localized shock waves which are transmitted to the adjacent area on the panel. The latter is supported at points remote from the contour forming explosive, so that the shock waves produce a rapid and localized substantially free-forming expansion of the panel in the adjacent areas, developing high strength corrugations. By virtue of localization of the expansion, the overall dimensions of the panel are not changed.

Employing this method, various shaped contoured panels, including high strength corrugated panels, are conveniently and economically manufactured. A limited number of contoured panels may be simply formed by placing the explosive adjacent the areas where the contours are desired. The contoured panels may also be formed after the panels are initially sized for assembly since the over-all dimensions do not change during the forming.

The invention and these and other advantages will appear more fully from the following description and accompanying drawings, wherein:

FIGURE l is a plan view of an apparatus for producing a corrugated panel by explosive forming of shaped charges in accordance with the invention;

FIGURE 2 is a section view taken along line 2 2 of FIG. 1;

FIGURE 2A is an enlarged section view taken on line 2A-2A of FIG. 1;

FIGURE 3 is a section view taken along line 3 3 of FIG. 1;

FIGURE 4 is an enlarged section View illustrating details of the apparatus of FIG. 1 and the method in accordance with the invention;

FIGURE 5 is a section View Corresponding to FIG. 2 illustrating an embodiment in accordane with the invention;

FIGURE 6 is an enlarged section view of a portion of the apparatus of FIG. 5 illustrating details of the embodiment and steps of the method in accordance with the invention;

FIGURE 7 shows form-ed panel corrugations and contains a graph providing evidence of operativeness of the method and apparatus of the invention; and,

FIGURES 8-13 illustrate applications for corrugated panels produced in accordance with the invention.

Referring to the drawings and more particularly to FIGS. 1-4 there is shown the basic method and apparatus for producing high strength corrugated panels by substantially free-forming of the panels with shaped explosive charges. Any suitable explosive, such as the strips generally designated 12, are placed on a pre-sized panel 14 of any ductile material, such as type 301 austenitic stainless steel, in a predetermined layout. They are placed in parallel in FIG. l directly against the panel 14 to produce the parallel `corrugations shown in FIGS. 7 and 8. EX- plosive is available at 20, 30, 40, 50, 60 and 100 Igrains per foot, and the concentration used depends on the thickness and material of the panel, depth and closeness of corrugations desired, and other factors which will become apparent. As an alternative, the explosive may be cast in sheet form with major concentrations of explosive delining a predetermined layout -to produce the corrugations of FIGS. 7 and 8. In this respect, it should be noted that the layout of explosive, whether in strip form or cast sheet form, may be designed to produce parallel corrugations or corrugations of any other predetermined pattern.

In this example, the concentration used was twentyive grains per foot. The panel was 16 gage austenitic stainless steel having a width of about forty inches, a length of about forty-two inches, and an average thickness of .050 inch, and was formed with the substantially uniform sinusoidal corrugations shown in FIG. 7, about 1/2 inch in depth on four inch centers, leaving about ten inches of flat plate area (not shown) on each side of the panel. FIG. 7 shows the variation in thickness in the panel following forming, averaging less than .002 inch with a maximum variation of .004 inch. Changes in width and length dimensions were negligible.

Referring again to FIGS. 1-4, a reinforced concrete base 16 is constructed having a plate 18 secured to the upper surface thereof and made substantially horizontal. Experience has shown that it is desirable to maintain the level of the plate within a tolerance of 1/16 inch. Half rounds 2l) are suitably supported on the plate 13 spaced from the upper surface of the plate and from each other. In this example, the half rounds are on 4 inch centers, are parallel to each other and have a diameter in the order of two inches. Their spacing from the surface of the plate is sufficient such that contact of the panel 14 downwardly with the plate under the force of explosive is avoided; i.e., expansion of the panel is substantially free-forming.

The panel 14 to be formed is placed on top of the half rounds, and intermediate the half rounds, also on four inch centers, the explosive strips 12 are located on top of the panel. A thin gage polyethylene sheet 22 is then laid over the panel and explosive and is backed up by loose end bars 24 forming a continuous dam adjacent the periphery of the panel 14. A suitable force transmitting fluid 26, for instance water, fills the inside of the dam covering the explosive strips 12.

At opposite ends of the spaces 28 between half rounds 20, Ts 30 fill the span between the half rounds and abut the underside of the panel 14, extending between the panel and the surface of plate 18. As shown in FIG. 3, the Ts are provided with rounded leading edges 32 facing inwardly towards spaces 28, their purpose being to assist in the formation of the corrugations and to avoid the formation of sharp edges.

The ends of charges 12 may be extended over the flat surfaces of the Ts for the purpose of holding down the panel on detonation. Additional hold-down charges 36 should be used over the outermost or end half rounds 38 for the same purpose, and if desired, intermediate charges 34 (FIG. 2A) may be used over the intermediate half rounds for this purpose. As mentioned above, the panel is dimensioned so that the end half rounds 38 preferably are at least ten inches inside of the ends of the panel, Experience has shown that this dimension is instrumental in avoiding panel shrinkage. By the same token, providing a distance between the ends of the corrugations and the panel side edges of about ten inches avoids distortion and side to side shrinkage.

At this point it should be noted that only a relatively small overall amount of hold-down explosive is used as compared to the overall amount of explosive used in forming strips 12, to prevent pull-in along the edges of the panel and consequent panel shrinkage. In this example, a charge concentration of twenty grains per foot sufiiced. Generally, the intermediate hold-down charges will be in the order of twenty grains per foot,

On the method of FIGS. l-4, it should be noted that the panels were first dimensioned and laid out for length, number and location of corrugations, and the explosive strips 12 were dimensioned, sized and located according to layout, in parallel alignment, although other patterns are within the scope of this application. The parallel alignment is necessary to obtain a sinusoidal configuration. In placing the panel on the half rounds, the explosive strips 12 should coincide with the center lines of the short Ts 30, with preferably an overlap of the strips on to the Ts, for the purpose of providing additional hold-down. Where a shallower corrugation is desired, about one inch of clear space may be provided between the ends of the explosive and the T inboard ends 32.

Following set-up of the assembly, the explosive forming and hold-down strips are simultaneously detonated by suitable equipment 4t) (FIG. 3), the detonation traveling at the same rate down the length of each charge progressing from common charge ends 42. Pressure waves are transmitted through the liquid transmitting medium 26 to the panel 14 along parallel paths corresponding to the charge positions. The impacting waves simultaneously produce uniform corrugateddepressions 44, shown in dotted lines in FIGS. 2 and 4, which are substantially free-formed except at the inboard ends of Ts 30.

As a result of the linear shape of the charges and the proximity of the charges to the panel, the impacting pressure waves are localized relative to the panel expanding only those portions of the panel directly adjacent the charges. Also, due to the narrow width of the charges relative to the overall panel dimensions and the localized and rapid strain rate expansion, the overall dimensions of the formed sheets after detonation remain the same as they were prior to detonation. No clamps are required to inhibit overall dimensional changes in any respect.

FIG. 4 shows further details in the construction of the half rounds and supports therefor, Elongated support blocks 46 are welded or suitably held on plate 18 and the half rounds 20 are bolted to the blocks.

Other modes of construction are suitable in accordance with the invention to allow for a substantially free-formed corrugation, for instance the apparatus of FIGS. 5 and 6. In this embodiment, a reinforced concrete foundation 50 is constructed having a plurality of parallel closely adjacent V grooves 52, on four inch centers, provided with steel plate cladding 54 to align pipes 56. The level of the foundation is again maintained within a tolerance of i1/16".

Two inch diameter pipes 56 are placed in the V grooves and short Ts 58 are placed upright in the spaces 60 between the pipes in positions corresponding to the terminus or end of each corrugation. The inboard ends of the short Ts are suitably rounded to prevent the Ts from cutting into the panel during forming. On the left and right ends of the panel 62, the first and last Ts 64 and 66 extend substantially the full length of the foundation. In effect, these long Ts will be about four inches or one corrugation width from the first and last corrugations made in the panel. The upper surfaces of the Ts and pipes coincide in altitude.

The panel 62 to be formed is placed over the pipes and Ts resting against both, and is located so that all lengths of explosive 68 coincide with the center lines ofthe spaces between the pipes (or center lines between opposed short Ts). Again, the short Ts preferably are located so that there is a slight overlap between the ends of the explosive and inboard ends of the Ts. The end lengths 70 and 72 of explosive are placed directly over the center lines of the long Ts, 64 and 66. An overow water dam 74 is placed over the work sheet, made up of a supporting frame as shown and the area within the dam is filled with water 76 to overflowing so that the level of water is about two inches.

Occasionally, a primacord charge will fail to detonate. Mistakes due to misfires can readily be corrected Without damage to adjacent corrugations by using wet sand as a transmitting medium. As an example, referring t0 FIG. 6, where the pipes 56 are on four inch centers, two small primacord strips 78 and 80 (20-25 grains per foot) are placed in parallel approximately a half inch apart along the center line between the pipes 56. A layer of moist sand 82 is placed over the strips, and the strips are detonated in the usual manner. Following detonation, it is difficult fby visual inspection to note the correction, and any difference in successive corrugations. In this respect, moist sand is preferred in that the charge force is slightly more localized.

FIG. 8 illustrates a roof panel for a large pressurized land -boiler made from an 18 gage carbon steel sheet by the method of the invention. The corrugations again are on four inch centers, and provide a sinusoidall configuration. An average flat area ten inches wide along each side of the panel was sufficient to avoid side and length dimensional changes in the panel during forming, although in this instance, the sides were sheared to provide the finished dimensions. The amount of flat area on each side of the panel is critical to avoid dimensional changes, but varies slightly depending upon thickness of the panel and depth, width and length of corrugations.

The corrugations make an angle of 10 with the sides of the panel, illustrating that any angle corrugation can be made. In this instance, the angle was selected for drainage reasons. It was found that the corrugations provide substantially greater strength against bending than does a conventional non-corrugated 11 gage flat plate. An essentially fiat upper surface facilitates use of insulation with the panel, and the reduced over all weight has the result that one man can install the panel, whereas, normal installation requires the presence of two men.

FIG. 9 shows seal plates made in accordance with the invention. These seal plates, also used in boilers, Imust resist high temperature service and corrosive conditions. 'Ihe seal plates were made of l1 gage corten steel and were corrugated to depths of 5A; inch to 3%; inch overall using the method of the invention. Explosive, having 60 grains per foot in a water depth of 3 inches, provided the desired force. The seal plates were subsequently oven tempered to reinstate their corrosion resisting properties, and were edge cut so that the corrugations run through to one edge while three edges remain flat. This provided a solution to the problem of cracking of the seal plates Although the invention has been described with a certain degree of particularity, it is understood that numerous changes in the details of construction and the combination and -arrangements of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A method for strengthening a metallic panel by explosively forming a plurality of elongated grooves in the panel, said forming being without the use of dies having the configuration of the panel so formed; comprising the steps of positioning the panel over a supporting structure, said structure including a plurality of elongated raised due to large temperature differences between the fixed 1.5 spaced apart supports having rounded upper surfaces, and free edges. the surfaces extending at least the lengths of the The application of FIG. l0 concerns drip lips used grooves desired and the upper surfaces thereof being in high temperature and highly corrosive boiler installaelevated above the rest of the supporting structure tions, designed to provide a run-off for liuid flowing into a distance greater than the depths of said grooves; a deaerator feedwater storage vessel. 'Ihe drip lips are 20 disposing explosive on the panel with at least a greater made of 304 annealed 11 .gage stainless steel, and in amount of explosive intermediate said supports and conventional applications consist of flat panels bolted extending at least the lengths ofthe grooves; along an upper edge to a suitable rigid support. Under detonating the explosive to form the grooves; high temperature service, the drip lips presently used have the amount of explosive intermediate the supports being a life expectancy of a few years due to a differential less than that which would cause the panel to come expansion between the main portion of the lips relative into substantial contact with said supporting structure the bolted edge. other than with the upper surfaces of said spaced By the invention, the drip lips are provided with corapart supports whereby the forming of the grooves is rugations in the main portion thereof and along the edge substantially free and unrestricted by said supporting removed from the bolted edge, which permits diiferential structure. expansion. Using conventional methods for making cor- 2. A method according to claim 1 wherein the detonatrugations, it would be necessary to make the corrugations ing explosive is in the form of elongated narrow strips the full length or width (depending on the direction in of explosive in juxtaposition with the panel and disposed which they extend) of the panels. By the invention, coralong a plane centered between the supports, the width rugations running along only the middle of the panel are of the explosive being narrow relative the overall dimenrnade, and then the panel is cut in half, as shown. In this sions of the panel to conne the explosive force substanway, a drip lip is provided having a fiat edge area for tially to the plane centered between the supports, bolting to the support with the rest of the sheet and lower further including additional elongated narrow strips of edge corrugated. explosive of narrow width relative the overall dimen- FIGS. 11-13 show a partition plate construction for 40 sions of the panel in juxtaposition with the panel and feedwater heaters, of the type described in application along parallel planes centered over said supports, Ser. No. 331,739, filed Dec. 19, 1963 by Edward Vogt, functioning to hold-down the panel, the method The plates are formed of 3 sections, welded together, two further including the step of detonating said addiend sections (FIG. 1l) and a middle section (FIG. 12). tional strips of explosive simultaneous with the The added strength afforded by the corrugations perdetonation of the first-mentioned strips of explosive. mits the use of a thinner gage material than that conven- 3. A method according to claim 1 wherein said elontionally used. This in turn reduces stress concentrations gated supports are in parallel alignment and on at least along ylines of connection between the partition plate four inch centers; and heater shell, the latter being of high strength relathe explosive intermediate said supports having a contively thick steel. eentration of at least 20 grains per foot suiicient to Tests have shown that uniform repeatable corrugations form substantially sinusoidal corrugations in said can be formed on ductile materials such as mild steel, low panel. carbon steel and corten steel, and stainless steel in thick- 4. A method according to claim 1 wherein said explonesses ranging from 18 gage (.049 inch) to 10 gage sive is detonated within a shock wave transmitting (0.1345 inch) with indications that the spacing of cormedium. rugations can be varied and the thickness of the material 5. A method according to claim 1 including the step of increased without dillculty. The shape of the panel to be supporting the panel between the spaced apart supports corrugated and non-uniformity in length requirements at the ends of the grooves to be formed to limit the present no problem. lengths of the grooves.

The following table is illustrative of corrugated panels G0 6. A method for corrugating metallic flat panels havmade in accordance with the invention. ing opposed ends comprising the steps of Explosive Depth of Spacing of Use lntended Plate Thickness Material Grains per Water Corrugation Corrugation Foot Depth (in.) (in.) to Q (in.)

11 Gage (.120 in) corten 60 1.5 GA 4 o Low Carbon Steel 2 4 do Carbon SteeL... 50 2% 4 18 Gage (.049 in o 25 4 Boiler Drip Llps 11 Gage (.120 in.) No. 304 Stainless Steel 100 3 %1 4 Boiler Seal Plates do Corten Steel 60 3 4 Pass Partition Plates for Condensers 10 Gage Low Carbon 60 3 Vg 4 Pressurized Boiler Panel 2 16 Gage (.065 in.) No. 321 Stainless Steel 60 2 1 4 lReslsts 20 p.s.i. differential better than present in. flat plate.

2 Resists 160 inches water pressures without excessive bowing.

horizontally leveling the panels on a supporting structure including a plurality of elongated parallel spaced apart supports having rounded upper surfaces, the supports extending at least the lengths of the corrugations desired and -being in side-by-side relationship between the panel ends, the upper surfaces of said supports further being elevated above the rest of the supporting structure a distance greater than the depths of the panel corrugations;

disposing a first series of continuous concentrations of explosive on the panel intermediate said supports having a charge concentration of at least 20 grains per foot, the concentrations of explosive being at least coextensive with the lengths of corrugations desired;

providing additional supports spaced from said parallel supports and from the panel ends but between the spaced supports and panel ends;

disposing a second series of continuous concentrations of hold-down explosive over said additional supports;

. simultaneously detonating the first and second series of explosive;

the improvement comprising detonating only limited amounts of explosive so that forming of the grooves is substantially free and unrestricted by the supporting structure.

7. A method of explosively forming a narrow contour in a ductile panel, comprising the steps of disposing an elongated continuous strip of explosive charge in juxtaposition with the panel, the width of the strip being small relative the over-all dimensions of the panel,

supporting the 'panel over a supporting structure including a plurality of raised spaced apart supports so that the portions of the panel adjacent the explosive strip are in spaced relation with the supports, the upper surfaces of the supports being elevated above the rest of the supporting structure a distance greater than the depth of said contour,

detonating the explosive strip from one end of the strip to cause the explosive to travel down the length of the strip thereby progressively forming a contour in the panel along the portions of the panel adjacent the strip, wherein only a limited amount of explosive is detonated so that forming of the contours is substantially free and unrestricted by the supporting structure.

8. A method according to claim 7 further comprising the steps of contours in a ductile panel, comprising the steps of disposing a rst series of elongated continuous parallel strips of explosive charges in juxtaposition with the panel, the width of the strips being small relative the overall dimensions of the panel,

supporting the panel over a supporting structure including a plurality of raised spaced apart supports so that the portions of the panel adjacent the explosive strips are in spaced relation with the supports, the upper surfaces of the supports being elevated above the rest of the supporting structure a distance greater than the depths of said contours,

simultaneously detonating the explosive strips and initiating detonation of each strip at a point of intersection between the strip and a line which is perpendicular to all the strips to cause the explosions to travel uniformly down the strips thereby progressively forming parallel contours in the panel along portions of the panel adjacent the strips, wherein only a limited amount of explosive is detonated so that forming of the contours is substantially free and unrestricted by the supporting structure.

10. A method of explosively forming parallel contours to form a sinusoidal conguration in a ductile panel, comprising the steps of disposing elongated continuous parallel strips of explosive charges in juxtaposition with the panel, the width of the strips being small relative the over-all dimensions of the panel, the strips further being equal distances apart and having an equal number of grains of explosive per foot of strip;

supporting the panel over a supporting structure including a plurality of raised spaced apart supports so that the portions of the panel adjacent the explosive strips are in spaced relation with the supports, the supports being intermediate the strips, the upper surfaces of the supports further being elevated above the rest of the supporting structure a distance greater than the depths of said contours;

simultaneously detonating the explosive strips and initiating detonation of each strip at a point of intersection between the strip and aline which is perpendicular to all the strips to cause the explosions to travel down the strips thereby progressively forming sinusoidal parallel contours in the panel along portions of the panel adjacent the strips wherein only a limited amount of explosive is detonated so that forming of the contours is substantially free and unrestricted by the supporting structure.

11. Apparatus for explosively forming metallic panels comprising a substantially horizontal base;

a plurality of elongated spaced apart supports each having a rounded upper surface, the support upper surfaces spaced from said base and defining a substantially horizontal plane;

additional support means in said plane spanning the spaces between the spaced apart supports at the ends of predetermined distances corresponding to the lengths of grooves desired in the panel, the additional support means having rounded inwardly facing edges;

the plane of the support upper surfaces being spaced a distance from the base sufficient such that grooves in the panel intermediate the supports are substantially free formed.

12. Apparatus according to claim 11 wherein said spaced apart supports are parallel and on at least four inch centers.

13. A method for forming corrugated steel panels having a panel thickness less than 0.25 inch, the corrugations being less than one and one half inches deep, comprising the steps of horizontally positioning a flat panel so that it rests against a plurality of elongated parallel spaced apart supports having rounded upper surfaces with approximately a one inch radius, the supports extending the lengths of the corrugations desired and being raised suiciently so that the corrugations are substantially free formed;

disposing a irst series of continuous concentrations of explosive on the panel having a charge concentration of at least 20 grains per foot, the charge concentrations being at least coextensive |with the lengths of. corrugations desired and intermediate said supports;

disposing a second series of continuous concentrations of explosive on the panel having charge concentrations of at least 20 grains per foot, the second series of concentrations being over lines of contact of said supports and panel, at least two of said second series of concentrations being between the panel ends and the cndmost corrugations;

simultaneously detonating the explosive concentrations from one end thereof to cause the explosions to travel the lengths of the concentrations thereby progressively forming a plurality contour in the panel, the concentrations of explosive being separate from one another and narrow relative the distance from crest to crest ofthe panel contours.

14. A method according to claim 13 wherein said supports are in parallel relationship and on approximately four inch centers to produce corrugations having a substantially sinusoidal conguration.

15. A method according to claim 13 wherein the endmost corrugations are at least about ten inches from the panel ends.

References Cited UNITED STATES PATENTS 2,935,038 5/1960 Chatten 72-56 3,060,879 10/ 1962 Staba 72-56 3,120,827 2/1964 Abegg 72-60 3,238,753 3/1966 Benatar 72-56 RICHARD I. HERBST, Primary Examiner.

10 K. C. DECKER, Assistant Examiner. 

